The day I stepped into Haske van Zadel-hoff’s store in Gulpen, the Netherlands, was the day I fell in love with historic buildings and the materials and methods with which they were built. That day was more than 20 years ago, and it changed the trajectory of my whole career.

I grew up in the province of Limburg, surrounded by a very distinctive building vernacular. The historic buildings found in Limburg are akin to the fachwerk properties in neighbouring Germany and Belgium. Haske van Zadelhoff is the expert in the restoration and preservation of this kind of building, and even on that first visit I realized how much I could learn from him. In no time at all, I’d convinced Haske to give me a job in his store and handed in my notice at my corporate job. Over the next three years, Haske taught me everything he knew about the way moisture flow works in old buildings and how the use of appropriate materials like lime plaster, lime washes, and clay help buildings to breathe and survive.

Throughout this time, there was one product in particular that really captivated me: linseed oil paint. I was particularly interested in the fact that so few people seemed to use it. Even historic building experts would happily use conventional film-forming plastic paints on wooden surfaces. This baffled me, and I set out to do my own research on wood treatments to determine not only which were the most historically accurate but also which were the most beneficial for historic materials.

One of the main focuses of my research was understanding the reasons so many buildings had crumbling plaster and rotting timber when they had previously survived for many centuries without any of these issues. It will probably come as no surprise to learn that the decay of historic timber came hand in hand with the introduction of synthetic petrochemical paints and wood treatments. First pioneered in the 1930s, the acceleration of anything plastic based was largely driven by available resources. The abundance of acrylics, latex, and alkyds as a result of the waste products of the war ma-chine coincided perfectly with an increased demand for anything new. The rebuilding of war-torn Europe was therefore dominated not only by the use of plastic paint, but also by concrete
cement largely replacing lime, and steel and structural glazing becoming common building materials.

Fortunately, some countries held on to traditional materials, which helped them to survive. Linseed oil paint was traditionally found anywhere flax was grown. In Europe, the epicentres for this were southern Sweden, Ger-many, Denmark, northern England and North-ern Ireland. Even though these countries have retained some usage of linseed paint, huge amounts of knowledge have been lost. I’ve spent the last two decades reading any historical text about linseed oil paint that I’ve been able to get my hands on. My library now includes more than 50 historic volumes, including information not only on how linseed oil paint was tradition-ally made, but also how it was used and applied. (As a side note here: you may have picked up on the fact that I use the terms “linseed oil paint” and “linseed paint” interchangeably. This is on purpose. In the US and Canada, the product is referred to as linseed oil paint, whereas in Eu-rope it tends to be called simply linseed paint.)

Unfortunately it wasn’t just knowledge of linseed paint that was dying out, but so was the actual product. To meet this need, I eventually began producing linseed paint myself. My aim has always been from the beginning to produce a high-quality linseed oil paint that could be made on a commercial scale, which would mean it would no longer be available only to very few specialists. Linseed oil paint should be available in consistent, high-quality batches for use not just on historic timber, but also any new buildings we erect. It’s also important to me to ensure that as much information as possible is available about linseed paint for as wide an audience as possible. For several years, I have been traveling abroad to deliver “Demystifying Linseed Paint” presentations to architects and other building industry professionals.

Any discussion of this paint must begin where the production process started for me: in finding the highest-quality linseed oil. Linseed oil is derived from pressing the seeds of the diversely useful flax plant (Linnum usitatissimum). There are a number of varieties of flax, but generally, the tall variety gets used for the production of linen and the shorter variety for the production of linseed oil. Flax grows best in loamy soil in a temperate climate with relatively high humidity. Growing conditions are important to the final quality of the linseed oil, but even more vital is the way the oil is pressed. The best quality linseed oil is cold-pressed. However, in large industrial oil production, it’s common to hot-press or add chemicals in order to eke out every last bit of potential usable oil and get a higher yield. These methods provide a very low-grade oil that is full of proteins and other ingredients, making the oil unsuitable for use in a high-quality paint. The more impurities the linseed oil contains, the higher the chance of early degradation.

When my company began the process of making linseed paint, we could have imported high quality oil from Sweden or Denmark, but this seemed counter-productive when the north of England has perfect growing conditions and an impressive historic track record in the growing of flax. Sometimes planets align, and I learned that a local farmer was already producing some of the finest linseed oil available. They were selling it under the name of flax oil (linseed oil is usually referred to as this when it is used in food) because they supplied it to the equestrian market as a food additive for show horses. Because the farm was used to producing a food-grade level of oil, their standard was as high as mine. Food-grade oil has to be filtered multiple times, which is done using actual meshes rather than ‘washing’ the oil with chemicals. This meant the starting point of the raw linseed oil we chose to work with could not have been better. We then set about finessing our own boiling process.

Even though linseed oil is classified as a drying oil, raw linseed oil does not actually dry very well and is not a very good carrier for pigments. If you were to attempt to grind pigments into raw oil, it would be very difficult to make sure every grain was encased in oil. Therefore, it’s necessary to boil it. Contrary to common belief, this isn’t necessarily done to re-move moisture. When we boil our raw oil, the water evaporation is less than 0.5 percent. We boil in the old, time honoured fashion of using an actual boiler, rather than “boiling” by mixing the oil with chemicals, which is the usual modern method Largely, I had to develop my own method for doing this through a process of trial and error, as it’s surprisingly hard to find descriptions of the old methods, tools, and temperatures used. Most historic texts jump straight to the description of the grinding of the paint or usage of pigments. I presume this is because the process was once such common knowledge that people did not feel the need to write it down. Eventually, after going through quite a lot of pans, I figured out a timing and temperature that worked. No natural ingredient is perfectly consistent however, so this is only a general guide – each batch needs tweaking.

When it’s used on its own, linseed oil (either raw or boiled) is not particularly suitable for use outdoors, as it does not offer much protection against UV breakdown. Of all the elements that exterior paint must withstand (including wind, rain, pollution and UV), sunlight is by far he most aggressive. Our forefathers discovered thousands of years ago that mixing earth into the oil makes the resulting wood treatment far more durable and longer lasting. Traditionally, pigments were mixed into oil using a muller and slab: a glass or smooth stone was used as a base to grind powder pigments into a smooth paste with a glass muller. This is the same method the old masters used. Centuries ago, artists had whole crews mixing and grinding oil and pigments for their paintings. During the Industrial Revolution, steam-driven, triple-roll-er mills started replacing the muller-and-slab technique. This meant that linseed paint could be manufactured on a far bigger and more eco-nomic scale. It also meant that paint began to be made in far more places than the heartland of the UK, France and Germany. Within only two or three generations of the Mayflower arriving in Plymouth, flax and linseed oil were being produced on a large scale in Virginia. We use triple-roller mills to mix our paint, though they are obviously no longer operated by steam.

In the art world, pretty much any possible pigment was and still is used in linseed paint. What started with just raw earth pigments (ochres, siennas, umbers, and oxides) developed over the centuries to a much larger list including animal and vegetable pigments. Some of the best-known examples of animal pigments are probably bone black and cochineal, while vegetable pigments are not only direct derivatives of plants like indigo, but also carbon black from charcoal. The Industrial Revolution saw an explosion of man-made products, including metal-based pigments such as Prussian blue or pigments derived from industrial processes like lamp black. While most pigments work well in a water-based medium, not all pigments disperse well in linseed oil. With a more limited selection of pigments to work with, getting the correct colour requires experience. Using only historically accurate ingredients and methods also means that the feel and character of the paint is automatically historically correct. There is no ap-proximation or imitation happening, as is the case with plastic paint that’s made using synthesized colorants.

We do not use all the pigments that would’ve been used in linseed paint historically. One pigment that seems to have become synonymous with linseed paint is lead white. Even though the harmful side effects of breathing in lead dust was already well known in the Middle Ages, the use of lead white didn’t stop in Europe until the early 1900s and it wasn’t banned in domestic settings in the US until 1978.  Despite the prevalence of lead poisoning amongst painters, lead white remained in common use for so long because it creates such a hard-wearing, durable paint. There simply wasn’t a good alternative until zinc and titanium were developed.

There’s a hardcore group of preservation specialists who still swear by lead white, but the reality is that the right proportion of zinc and titanium offers 90% of the efficacy lead white used to, without any of the health hazards. Additionally, there are other benefits to the new pigments: zinc white has excellent anti-mould properties. Using the right ingredients in the right way means that there’s no reason that linseed paint would have a higher risk of mould growth than modern paint.

When considering health hazards, we can-not ignore the deep wounds that plastics are inflicting on our precious planet. Most people do not realize that the modern paint they buy from the hardware store and use on their walls is nothing but coloured, liquid plastic. Not only does this paint off-gas for nearly five years, it is also a significant contributing factor to plastic waste. A recent study by Environmental Action shows that a staggering 58 percent of all microplastics in the ocean are from paint. What is even more shocking about this is that the majority of these microplastics come not from industrial applications, but from accumulated domestic use. While this is a sobering fact, it does mean that we can all help make a difference in significantly reducing this number. Imagine how this would be improved if we all went back to using lime wash, clay paint, and linseed oil paint; all made from raw earth ingredients that will eventually be comfortably reabsorbed by mother nature.

This circular, “cradle-to-cradle” production ideal is what I firmly believe we should be striving for, but it is also something that unfortunately already seems to have been hi-jacked for commercial gain. Accreditation for a cradle-to-cradle certificate starts at around £10,000, which undermines the whole essence of the ambition. This is not just a problem for this particular accreditation: green-wash-ing is endemic in the industry. The term “water-based” is particularly misleading, and is now used by all major plastic paint manufacturers. “Water-based” does not actually mean the paint is water based – it just means that you can add water to the latex or acrylics. The only truly water-based paints are lime washes and distempers.

There is an opportunity here to learn a very valuable lesson from our forefathers and make their knowledge part of the solution to some of the enormous problems faced by the planet. We can only hope that the building industry will slowly begin to recognize that historic building materials such as linseed paint and lime wash-es are not only historically accurate and longer-lasting, they also have only a fraction of the carbon footprint of man-made materials.

For more information, check out the book Linseed Paint & Oil, a guide to traditional production and application methods